Evidence of Possible Coupling Between Circadian Oscillators of the Mouse Lung

by Carver, Paula D.

Abstract (Summary)

Circadian rhythms in gene expression have been detected in almost every organ of mammals, including the lung. These rhythms appear to optimize daily physiological functions and are regulated by peripheral circadian oscillators in the organs. A major circadian pacemaker in the suprachiasmatic nucleus of the hypothalamus also controls the timing of the peripheral oscillators in part though the vagus nerve. This study provided evidence of possible coupling between circadian oscillators in lung tissue maintained in culture. It also tested whether acetylcholine treatments would mimic timing signals from the vagus nerve. Circadian rhythms in gene expression were monitored by imaging the bioluminescence from lung cultures made from mice that contain the mPer1::luc transgene. Acetylcholine at 50 µM had no affect on the period, phase, or luminescence intensity of the lung cultures. Maps of the period and phase of rhythms in the cultures were determined at each pixel of the bioluminescence images. The most frequent periods were 19.50 and 25.75 hours in cultures from two mice. The spatial distribution of phases found in the maps showed a clustering, and these phases were compared with the timing of the prior light cycle experienced by the mice. Phases ranged from one hour after dusk to one hour after dawn, in agreement with previous studies that identified an average peak in the lung circadian rhythm during the night. Changes in phase distributions between circadian cycles suggested that lung oscillators may interact to maintain a closely coupled state. Desynchrony between these oscillators could play a role in diseases of the human lung.